UNIVERSITY  OF  CALIFORNIA   PPBLICATIONS 

COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 
BERKELEY,  CALIFORNIA 


COMMERCIAL  PRODUCTION  OF 
GRAPE  SYRUP 


BY 

W.  V.  CRUESS 


BULLETIN  No.  321 

May,  1920 


UNIVERSITY   OF  CALIFORNIA   PRESS 

BERKELEY 

1920 


David  P.  Barrows,  President  of  th3  University. 


EXPERIMENT  STATION  STAFF 

HEADS  OF  DIVISIONS 

Thomas  Forsyth  Hunt,  Dean. 

Edward  J.  Wickson,  Horticulture  (Emeritus). 

Walte  i  Mulford,  Forestry,  Director  of  Resident  Instruction. 

Herbert  J.  Webber,  Director  Agricultural  Experiment  Station. 

B.  H.  Crocheron,  Director  of  Agricultural  Extension. 
Hubert  E.  Van  Norman,  Vice-Director;  Dairy  Management. 

James  T.  Barrett,  Acting  Director  of  Citrus  Experiment  Station;  Plant  Pathology. 
William  A.  Setchell,  Botany. 
Myer  E.  Jaffa,  Nutrition. 
Charles  W.  Woodworth,  Entomology. 
Ralph  E.  Smith,  Plant  Pathology. 
J.  Eliot  Coit,  Citriculture. 
John  W.  Gilmore,  Agronomy. 
Charles  F.  Shaw,  Soil  Technology. 
John  W.  Gregg,  Landscape  Gardening  and  Floriculture 
Frederic  T.  Bioletti,  Viticulture  and  Fruit  Products. 
Warren  T.  Clarke,  Agricultural  Extension. 
John  S.  Burd,  Agricultural  Chemistry. 
Charles  B.  Lipman,  Soil  Chemistry  and  Bacteriology. 
Clarence  M.  Haring,  Veterinary  Science. 
Ernest  B.  Babcock,  Genetics. 
Gordon  H.  True,  Animal  Husbandry. 
Fritz  W.  Woll,  Animal  Nutrition. 
W.  P.  Kelley,  Agricultural  Chemistry 
H.  J.  QuAYLE,  Entomology. 
Elwood  Mead,  Rural  Institutions. 
H.  S.  Reed,  Plant  Physiology 
L.  D.  Batchelor,  Orchard  Management. 
J.  C.  Whitten,  Pomology. 
IFrank  Adams,  Irrigation  Investigations. 

C.  L.  RoADHOUSE,  Dairy  Industry. 
R.  L.  Adams,  Farm  Management. 

F.  L.  Griffin,  Agricultural  Education. 
John  E.  Dougherty,  Poultry  Husbandry 
L.  J.  Fletcher,  Agricultural  Engineering. 
Edwin  C.  Voorhies,  Assistant  to  the  Dean. 


fin  co-operation  with  office  of  Public  Roads  and  Rural  Engineering,  U.  S.  Department  of  Agriculture . 


COMMERCIAL  PRODUCTION  OF  GRAPE  SYRUP 

By  W.  V.  CKUESS 


Since  the  publication  of  Bulletin  803  of  this  Station*  in  1918, 
marked  progress  has  been  made  in  methods  of  preparing  grape  syrup. 
Because  of  this  fact  and  on  account  of  the  widespread  interest  of 
grape  growers  in  the  subject,  the  present  publication  has  been  pre- 
pared to  supplement  the  information  given  in  the  bulletin  cited  above. 

Syrup  was  produced  from  wine  grapes  and  table  grape  culls  in 
commercial  quantities  by  several  factories  during  the  past  season. 
Although  certain  difficulties  were  encountered,  these  w^ere  overcome 
and  the  product  was  marketed  successfully,  demonstrating  that  the 
manufacture  of  syrap  offers  a  practical  method  of  utilizing  a  large 
proportion  of  the  state's  wine  grapes.  However,  it  is  recommended 
that  all  other  methods,  such  as  evaporation  and  grape  juice  manu- 
facture also  be  employed,  because  it  will  not  be  possible  during  the 
next  season  to  convert  the  whole  crop  into  syrup. 

Several  different  types  of  syrup  have  been-^produced.  Of  these,  the 
following  are  most  promising:  (1)  a  syrup  of  deep  violet-red  color  and 
rich  berry-like  flavor  made  in  vacuum  pans  of  standard  design;  (2)  a 
syrup,  red  or  white  as  desired,  made  by  concentrating  fresh  Muscat 
or  other  highly  flavored  juice  by  the  freezing  process  and  blending  this 
with  a  syrup  of  high  sugar  content  made  by  the  vacuum  pan  process ; 
(3)  a  red  or  white  syrup  made  in  a  proprietary  patented  vacuum  pan 
so  designed  that  part  of  the  natural  grape  flavor  is  condensed  and 
returned  to  the  syrup.  These  different  varieties  will  be  discussed  in 
the  order  given  above. 

EED  GRAPE  SYRUP  BY  STANDARD  VACUUM  PROCESS 

It  is  believed  that  the  manufacture  of  this  syrup  offers  a  greater 
posvsibility  of  utilizing  a  large  proportion  of  the  wine  grape  crop  of 
the  state  than  does  any  other  one  grape  product,  for  the  following 
reasons:  It  requires  only  the  use  of  present  winery  machinery  plus 
vacuum  pan  equipment  of  the  kind  already  installed  in  some  wineries. 


*  Grape  Syrup:   a  Preliminary  Report,  by  P.  T.  Bioletti  and  W.  V.  Criiess, 
Bulletin  303,  California  Agricultural  Experiment  Station. 


402  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

Many  former  winemakers  are  trained  in  the  nse  of  such  vacuum  equip- 
ment and  g'rape-handling  methods,  so  that  the  training  of  specialists 
will  not  be  necessary.  The  equipment  is  standardized  and  produced 
by  a  number  of  firms  and  therefore  may  be  had  before  the  coming 
season.  No  patent  rights  are  violated  in  making  this  syrup.  There- 
fore, any  one  may  undertake  its  production.  During  the  past  season 
syrup  of  this  type  has  sold  at  wholesale  in  many  instances  for  more 
than  three  dollars  per  gallon.  This  price  represents  from  $125  to  $150 
gross  for  the  product  from  a  ton  of  fresh  grapes;  or  is  about  the 
equivalent  of  20c  per  pound  for  raisins  made  from  grapes  of  the 
same  quality. 

Equipment  Necessary. — The  following  list  includes  the  essential 
items  of  equipment : 

1.  Crusher  and  stemmer  (now  installed  in  all  wineries). 

2.  Basket  or  rack  and  cloth  press  (old-style  continuous  press  not 
satisfactory). 

3.  Device  for  heating  crushed  grapes  for  color  extraction. 

4.  Tanks  and  vats  for  leaching  pomace  and  storing  juice  and  syrup. 

5.  Filter  or  filter  press. 

6.  Vacuum  pan  fitted  with  a  barometric  condenser  and  dry  vacuum 
pump  or  a  pump  only  which  will  maintain  a  twenty-eight  to  twenty- 
nine  inch  vacuum  during  operation  of  pan. 

7.  Can-sealing  machine  or  bottling  machine.  Barrels  may  be  used 
for  bulk  goods. 

Grapes  for  Red  Syrup. — All  varieties  of  wine  grapes  may  be  used. 
A  syrup  of  intense  red  color  can  be  m.ade  even  if  50  per  cent  of  the 
grapes  used  are  of  white  varieties.  The  grapes  should  be  thoroughly 
ripe  to  obtain  the  highest  yields  and  best  quality.  Moldy  or  fermenting 
grapes  give  an  inferior  product. 

Crushing  and  Stemming. — These  operations  are  carried  out  as  for 
wine  making.  Stems  should  be  well  removed  in  order  to  prevent  the 
syrup  becoming  too  astringent  in  flavor. 

Heating  to  Extract  Color. — The  color  of  grapes  is  located  in  the 
skins  and  does  not  dissolve  in  the  juice  unless  the  grapes  are  heated 
sufficiently  to  cause  the  '  ^  color  to  flow. ' '  The  color  will  dissolve  slowly 
at  105°  F.  to  120°  F.  and  almost  instantly  at  160°  F.  to  170°  F.  The 
higher  temperatures  have  proved  most  satisfactory  from  the  practical 
standpoint,  although  a  better  flavored  product  is  obtained  at  the  lower 
temperatures. 

Iron  should  not  be  permitted  to  come  in  contact  with  the  juice  during 
lieating,  because  it  dissolves  rapidly,  injuring  the  flavor  and  color. 


Bulletin  321 


COMMERCIAL  PRODUCTION  OF  GRAPE  SYRUP 


403 


Copper  dissolves  to  a  slight  extent;  it  is  doubtful  whether  injurious 
amounts  of  this  will  dissolve  during  heating  of  the  crushed  grapes. 
Aluminum,  tin,  ^'Monel"  metal,  or  silver-plated  copper  may  be  used 
safely. 

Tin-lined  copper,  glass-lined  steel,  or  plain  aluminum  steam- 
jacketed  kettles  have  all  been  successfully  used. 

Many  different  forms  of  heaters  have  been  used  in  commercial  prac- 
tice. Vats  fitted  with  steam  coils  have  been  used  but  are  difficult  to  stir 
and  to  empty.    The  simplest  heater  observed  consisted  of  a  1500-gallon 


Fig.  1. — Simple  form  of  steam  injector  used  in  the  Greco  Company's 
cannery  at  San  Jose  to  heat  crushed  grapes. 

tank  in  which  was  placed  a  large  two-way  fitting  2i/^-inch  or  3-inch 
size  attached  to  an  overhead  steam  line,  and  with  fitting  left  open  at 
sides  and  bottom.  When  steam  is  passed  through  this  device  into  the 
crushed  grapes  it  acts  as  an  injector,  drawing  the  juice  and  grapes 
through  the  side  openings  and  forcing  them  out  through  the  bottom 
opening.  This  also  stirs  the  grapes  thoroughly.  Aluminium  or  other 
resistant  metal  (not  iron)  must  be  used.  The  tank  must  be  placed 
above  the  level  of  the  press  baskets  and  equipped  with  a  large  outlet 
and  chute  to  permit  rapid  emptying  of  the  contents  into  the  press 
baskets. 

The  crushed  grapes  must  be  stirred  to  prevent  overheating  and  to 
accomplish  uniform  and  rapid  heating. 


404  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION 

As  soon  as  a  thermometer  suspended  in  the  crushed  grapes  indicates 
a  temperature  of  160°  F.  to  170°  F.  the  heated  grapes  must  be  trans- 
ferred at  once  to  the  press.  A  juice  of  better  flavor  and  of  as  deep 
color  can  be  obtained  by  heating  the  crushed  grapes  to  only  110°  to 
120°  F.,  transferring  to  wooden  vats  and  allowing  to  stand  overnight. 
This  lower  temperature  is  less  injuriors  to  the  flavor,  but  is  more 
troublesome  to  apply. 

Another  system  that  has  been  used  is  to  crush  the  grapes  into  open 
vats,  drain  off  the  juice,  heat  the  juice  to  165°  F.  to  170°  F.  and 
return  it  to  the  crushed  grapes.  This  is  continued  until  the  mixture 
reaches  the  desired  temperature.  However,  for  regular  commercial 
operation,  it  is  believed  that  the  injector  type  of  heater  will  prove  one 
of  the  most  practical  heating  devices. 

Pressing. — If  the  grapes  have  been  heated  to  160°  F.  or  higher, 
they  should  be  pressed  at  once  to  avoid  extraction  of  too  much  tannin 
from  the  seeds.  If  it  is  necessary  to  allow  the  grapes  to  stand  several 
hours  after  heating,  lower  temperatures  should  be  used. 

For  large-scale  operations  the  basket  type  of  hydraulic  wine  grape 
press  is  most  convenient  and  is  efficient.  Several  baskets  are  needed 
for  each  press  in  order  that  the  grapes  may  drain  well  before  pressing. 
Rack  and  cloth  presses,  such  as  those  designed  for  pressing  apples, 
are  used  in  eastern  grape- juice  factories  for  pressing  heated  grapes 
for  grape  juice  manufacture.  They  produce  very  high  yields  but 
require  more  labor  than  the  basket  press.  Small  syrup  factories  have 
used  hand  power,  basket  screw  presses,  but  these  are  too  expensive  to 
operate  upon  a  large  scale.  A  successful  continuous  press  has  recently 
been  developed. 

It  will  usually  be  desirable  to  line  the  press  basket  with  burlap  to 
prevent  the  grape  pulp  escaping  between  the  press  staves. 

Well-drained  heated  grapes  may  be  quickly  pressed  and  a  large 
yield  of  juice  obtained  because  heating  destroys  the  slimy  nature  of 
freshly  crushed  grapes  and  breaks  down  the  juice  cells. 

Extracting  Juice  from  Pomace. — The  press  cake  or  pomace  will 
amount  to  about  300  to  500  pounds  per  ton  of  grapes,  and  contains 
juice  equal  to  over  50  per  cent  of  its  weight.  This  juice  may  be 
recovered  by  leaching  the  pomace  with  water.  A  simple  method  is  to 
mix  the  pomace  with  sufficient  water  in  the  heating  tank  to  render 
the  mixture  plastic.  It  may  then  be  heated  to  about  120°  F.  and 
pressed.  This  dilute  pressed  juice  may  be  used  to  extract  a  second  lot  of 
pomace,  thereby  materially  increasing  its  sugar  content.  In  laboratory 
tests  a  liquid  containing  several  per  cent  of  sugar  was  obtained  by  a 


Bulletin  321         COMMERCIAL  PRODUCTION  OF  GRAPE  SYRUP  405 

second  extraction  of  the  pomace,  although  it  is  doubtful  whether  a 
second  treatment  would  be  made  in  commercial  practice. 

It  is  also  possible  to  extract  the  juice  from  the  pomace  by  the 
diffusion  process  used  in  European  countries  or  by  the  sprinkling 
method,  formerly  used  in  California  wineries. 

The  sugary  solution  obtained  from  the  pomace  should  be  con- 
centrated separately  from  the  juice  obtained  by  the  first  pressing 
because  of  the  inferior  quality  of  the  former. 

Clearing  the  Juice. — The  juice  from  the  press  is  cloudy  and  should 
be  made  clear  before  concentration  if  a  syrup  of  high  quality  is  to  be 
produced.  Straining  the  freshly  pressed  juice  through  screens  will 
remove  the  coarse  particles  of  pulp,  seeds,  etc.  Settling  twelve  to 
fifteen  hours  in  rather  shallow  tanks,  such  as  fermentation  vats,  will 
permit  much  of  the  suspended  matter  to  settle.  The  settled  juice  may 
be  drawn  off  the  sediment  and  filtered  through  a  wood-pulp  filter  of 
any  of  the  types  formerly  used  in  wineries.  The  pulp  used  should  not 
be  excessively  fine,  as  the  filtration  will  otherwise  be  very  slow  or 
impossible.  The  pulp  must  be  removed  and  washed  much  more  fre- 
quently than  where  wine  or  vinegar  is  filtered.  This  makes  the 
installation  of  ample  pulp-washing  machinery  and  a  large  stock  of 
filtering  pulp  necessary.  If  these  precautions  are  observed  it  will  be 
possible  to  filter  the  juice.  Wooden  frame  filter  presses  equipped  with 
coarse  cloths  will  probabl.y  give  good  results  and  large  capacity, 
although  preliminary  tests  by  one  grape  syrup  factory  and  by  a  sweet 
cider  factory  indicate  that  considerable  experimental  work  must  be 
done  before  thoroughly  satisfactory  results  can  be  obtained. 

The  sediment  from  the  settling  tank  may  be  filtered  in  bag  filters 
or  may  be  mixed  with  the  pomace  during  water  extraction,  when  part 
of  the  sediment  will  adhere  to  the  grape  skins  and  stems. 

Juice  may  be  clarified  by  the  addition  of  about  four  to  five  gallons 
of  a  solution  of  casein  containing  three  ounces  of  odorless  commercial 
casein  per  gallon.  This  solution  is  made  by  dissolving  a  weighed 
amount  of  the  casein  in  dilute  ammonia  water,  boiling  off  the  excess 
ammonia  and  diluting  with  water  so  that  each  gallon  contains  three 
ounces  of  casein.  This  solution  is  added  to  the  juice  and  thoroughly 
mixed  with  it.  It  will  settle  in  eight  to  twelve  hours  if  clarification  has 
been  successful  and  the  clarified  juice  may  then  be  filtered  very  easily. 

In  our  experimental  work  the  addition  to  each  100  gallons  of  juice 
of  about  eight  pounds  of  Spanish  Clay  previously  thoroughly  ground 
with  water  to  give  a  smooth  fine-grained  mud,  will  usually  produce  a 
rapid  clarification,  but  gives  a  large  amount  of  sediment. 


406 


UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION 


Clarification  will  usually  not  be  necessary  or  desirable,  but  may  be 
employed  if  a  brilliantly  clear  syrup  is  desired. 

Concentration. — If  grape  juice  is  boiled  down  to  a  syrup  in  an 
open  kettle  the  finished  product  will  be  dark  brown  in  color  and  of  a 
molasses  flavor  and  odor,  because  the  high  temperature  of  boiling  under 
atmospheric  pressure  caramelizes  or  scorches  the  grape  sugar.  If  the 
atmospheric  pressure  is  to  a  large  degree  removed  by  placing  the 
juice  under  a  vacuum  the  boiling  point  will  be  very  greatly  lowered, 
with  the  result  that  the  grape  sugars  are  not  caramelized,  much  of  the 


^/^ 


Fig.  2, — Chart  showing  relation  between  boiling  point  of  water  and 
vacuum  in  inches. 


fresh  grape  flavor  and  aroma  are  retained,  and  the  color  of  the  juice 
is  not  injured.  To  obtain  the  best  results  a  vacuum  of  at  least  twenty- 
eight  inches  should  be  employed,  as  this  will  give  such  a  low  boiling 
point  that  the  syrup  will  not  be  injured  appreciably.  The  relation 
between  the  boiling  point  and  degree  of  vacuum  as  indicated  by  the 
''inches  vacuum"  on  the  gauge  is  shown  in  the  above  chart. 

It  will  be  seen  from  the  chart  that  water  under  a  24  to  26-inch 
vacuum  (the  degree  of  vacuum  ordinarily  used  in  commercial  prac- 
tice) boils  at  about  140°  F.  to  125°  F.  Grape  syrup  will  boil  at  tem- 
peratures about  10°  F.  higher  than  these.    At  29  inches  vacuum  water 


Bulletin  321 


COMMERCIAL  PRODUCTION  OF  GRAPE  SYRUP 


407 


boils  at  about  75°  F.  and  syrup  at  about  85°  F. ;  temperatures  no 
higher  than  mid-day  temperatures  in  grape-growing  districts  during 
the  picking  season.  To  reach  such  a  high  degree  of  vacuum  a  "dry 
vacuum  pump"  in  combination  with  a  barometric  condensor  system 
will  probably  be  most  satisfactory.     A  wet  vacuum  pump  plus  a  dry 


COnOCN.'jCRi 


Fig.  3. — Pan  equipped  with  dry  vacuum  pump  and  barometric  condensor 
(courtesy  of  Ingersoll-Eand  Company). 

vacuum  pump  may  also  be  used,  but  cost  of  installation  and  operation 
will  usually  be  greater  than  with  the  barometric  system. 

The  barometric  condensing  system  consists  of  a  condensing  chamber 
connected  to  the  vapor  outlet  of  the  vacuum  pan  into  which  chamber 
above  the  vapor  entrance  is  led  a  jet  of  water,  the  vapors  from  the 
pan  being  condensed  by  contact  with  the  water  spray.    The  condensed 


408  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

vapors  and  water  flow  by  gravity  into  a  vertical  pipe  below  the  con- 
densing chamber.  This  pipe  is  over  31  feet  in  height  and  opens  into 
an  open  tank  or  hot  well  open  in  turn  to  the  air.  The  air  and  un- 
condensed  vapor  from  the  pan  rise  to  the  top  of  the  condensing 
chamber  and  are  removed  by  a  dry  vacuum  pump.  The  water  used  for 
condensing  the  vapors  from  the  pan  is  usually  supplied  by  a  circulat- 
ing pump  acting  independently  of  the  vacuum  pump.  Figure  3  illus- 
trates the  general  appearance  of  a  vacuum-pan  installation  consisting 
of  pan,  barometric  condensor,  dry  vacuum  pump,  hot  well,  and  circu- 
lating pump. 

In  addition  to  a  good  vacuum  pump  a  large  supply  of  water  for 
condensing  purposes  is  necessary  to  maintain  a  high  vacuum.  At 
28  inches  vacuum*  and  use  of  a  barometric  condensing  system,  approxi- 
mately 5.5  gallons  of  water  at  75°  F.  will  be  needed  to  condense  each 
pound  of  water  vapor ;  or,  over  forty  gallons  of  water  for  each  gallon 
of  water  evaporated  from  the  juice.  At  25  inches  vacuum  very  much 
less  water  and  at  29  inches  more  water  is  needed ;  that  is,  the  higher 
the  vacuum  the  more  condensing  water  is  needed. 

Where  the  water  supply  is  inadequate  the  water  from  the  condensor 
may  be  cooled  by  use  of  a  cooling  tower  or  spray  cooling  system  such 
as  used  in  many  industrial  plants,  thus  permitting  the  water  to  be 
used  over  and  over  again,  although  the  water  lost  by  evaporation  on 
the  cooling  tower  or  spray  must  of  course  be  replaced. 

The  vacuum  pan  may,  if  properly  equipped,  be  used  continuously, 
juice  being  allowed  to  flow  into  the  pan  continuously  and  the  syrup 
withdrawn  from  the  pan  continuously  by  a  special  pump.  However, 
according  to  0.  S.  Newman,  the  ordinary  syrup  pan  can  not  be  used 
in  this  way  except  under  a  vacuum  of  twenty-five  inches  or  less  because 
the  pump  usually  installed  will  not  operate  satisfactorily  against  a 
vacuum  of  twenty-six  to  twenty-nine  inches ;  but  it  is  very  probable 
that  this  problem  may  be  overcome  by  use  of  a  pump  of  proper  design. 

Some  operators  prefer  to  use  their  vacuum  pans  by  the  "batch" 
system;  that  is,  to  allow  juice  to  enter  the  pan  and  at  the  same  time 
concentrating  until  the  pan  contains  a  full  charge  of  syrup.  When 
this  reaches  the  desired  concentration  the  pan  is  emptied  and  a  new 
''batch"  started.  This  is  less  convenient  than  the  continuous  system 
and  reduces  the  capacity  of  the  pan,  but  probably  permits  more 
accurate  control  of  the  composition  of  the  syrup. 


Estimate  furnished  by  Jngersoll-Eand  Company. 


Bulletin  321 


COMMERCIAL  PRODUCTION  OF  GRAPE  SYRUP 


409 


The  syrup  should  be  concentrated  until  it  will  test  at  60°  F.  at  least 
68°  Balling,  or  68°  Brix,  if  it  is  to  be  held  for  more  than  a  few  weeks. 
We  have  found  that  syrup  of  65°  or  66°  Balling  will  soon  ferment 
and  become  moldy,  but  that  syrup  of  70°  Balling  will  keep  perfectly. 
Vacuum  pans  are  equipped  with  a  sampling  device  by  which  enough 
syrup  maj  be  removed  for  a  Balling  test.     The  Balling  hydrometer 


■JETSSiiiSiiiirs 


.vncuuM  PUMP 


5YRUP    P/iN 
THe  OSCHPIffiCUZ  COPPER   I  fffi/fSJ  WORK3  MC 


Fig.  4. — Sketch  of  a  vacuum  pan  showing  vapor  condensor  and  wet  vacuum 
pump  connection  (courtesy  of  Oscar  Krenz  Company). 


used  is  calibrated  from  0  to  70°  Balling.  A  Brix  hydrometer  of  the 
same  range  may  be  used  because  the  Brix  and  Balling  scales  are  prac- 
tically identical.  The  temperature  at  which  the  test  is  made  greatly 
affects  the  result ;  in  making  the  test,  a  thermometer  should  be  inserted 
in  the  sample  with  the  hydrometer  and  correction  made  accordingly. 
The  following  table  indicates  the  approximate  number  of  degrees 
Balling  or  Brix  to  add  to  the  reading  shown  by  the  hydrometer  in  a 
syrup  of  60  to  70  degrees  Balling  or  Brix. 


410  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Corrections  to  be  made  to  Balling  or  Brix  Readings  on  Account  of 

Temperatures 


Temperature, 
degrees  F. 

Degrees  Balling  or  Brix 

to  be  added  to 

hydrometer  reading 

Temperature, 
degrees  F. 

Degrees  Balling  or  Brix 

to  be  added  to 

hydrometer  reading 

64 

.0 

126 

2.9 

72 

.3 

130 

3.1 

75 

.4 

135 

3.4 

82 

.7 

140 

3.7 

86 

.8 

149 

4.2 

90 

1.1 

158 

4.3 

97 

1.4 

167 

5.2 

100 

1.6 

176 

5.8 

108 

1.9 

185 

6.3 

110 

2.0 

194 

6.9 

115 

2.3 

203 

7.5 

121 

2.6 

212 

8.2 

An  example  will  make  the  use  of  the  table  clear.  Suppose  that  a 
syrup  sample  from  the  vacuum  pan  tests  64°  Balling  or  Brix  and  the 
temperature  is  143°  F.  The  temperature  140°  F.  is  the  nearest  tem- 
perature given  in  table  and  the  correction  at  140°  F.  is  3.7°  Balling  or 
Brix ;  therefore,  the  approximate  corrected  reading  will  be  64  -|-  3.7 
=  67.7°  Balling  or  Brix. 

Cooling  the  Syrup. — When  the  syrup  reaches  the  desired  concen- 
tration it  may  be  drawn  off  and  stored  to  permit  separation  of  cream 
of  tartar  before  placing  in  final  packages  for  sale ;  or  it  may  be  drawn 
directly  into  cans  or  other  small  containers.  If  it  is  to  be  stored  in 
large  lots,  the  syrup  must  be  cooled  to  about  100°  F.  or  less,  in  order 
that  caramelization  of  the  flavor  and  browning  of  the  color  will  not 
take  place.  This  point  is  of  great  importance,  as  0.  S.  Newman*  has 
shown.  Mr.  Newman  uses  a  long  shallow  copper  pan,  around  the  sides 
and  bottom  of  which  is  circulated  cold  water.  The  syrup  is  cooled  as 
it  flows  over  the  surface  of  the  pan.  Probably  a  vertical  milk  cooling 
coil  would  serve  the  purpose. 

Storing  the  Syrup. — Cream  of  tartar  separates  from  the  syrup  and 
will  collect  on  the  sides  and  bottom  of  storage  tanks,  from  which  it 
may  later  be  recovered  as  a  valuable  by-product.  Where  storage  tanks 
are  available  and  clear  syrup  is  desired,  it  will  probably  be  advisable 
to  store  the  syrup  a  month  or  longer. 

Canning  or  Bottling  the  Syrup. — If  the  syrup  is  to  go  into  cans  or 
bottles  it  may  go  direct  from  the  vacuum  pan  to  these  containers, 
which  are  sc^aled  at  once  and  are  ready  for  shipment  to  market.     If 


*  O.  S.  Newman,  Manager  of  Woodbridgc  Vineyard  Association,  Woodbridge, 
California. 


Bulletin  321 


COMMERCIAL  PRODUCTION  OF  GRAPE  SYRUP 


411 


such  containers  are  used,  it  is  perfectly  feasible  to  concentrate  the 
syrup  only  to  64°  or  65°  Balling  or  Brix,  heat  it  to  150°  F.  near  the 
end  of  concentration  and  seal  it  hot  in  cans  or  bottles  to  destroy  yeasts 
and  molds.  The  yield  of  syrup  is  considerably  greater  at  65°  Balling 
than  at  70°,  but  it  will  not  keep  unless  sealed  hot  or  pasteurized  after 
sealing. 

Number  10  cans  and  gallon  cans  have  been  found  very  satisfactory 
as  syrup  containers  and  make  a  suitable  size  for  soda  fountain  or 
household  use. 


Fij 


[.  5. — Two  types  of  vacuum  pans.    On  left,  usual  form  of  grape  syrup  pan; 
on  right,  pan  equipped  with  stirring  device. 


Importance  of  Character  of  Lining  of  Vacuum  Fans. — Most  syrup 
pans  are  made  of  sheet  copper  and  the  juice  is  concentrated  in  contact 
with  this  metal.  Analyses  by  C.  H.  McCharles  and  R.  W.  Bettoli* 
have  shown  that  syrup  containing  sulfurous  acid  and  concenterated  in 
a  copper  vacuum  pan  may  contain  as  much  as  seventy-five  parts  per 
million  of  dissolved  copper,  although  in  most  syrups  concentrated  in 
this  way  the  amount  is  much  less.     Two  lots  of  syrup  made  in  copper 


*  The  writer  wishes  to  thank  Professor  McCharles  and  Mr.  Bettoli  for  these 
valuable  data. 


412  UNIVERSITY    OF    CALIP^ORNIA EXPERIMENT    STATION 

pans  from  unsulfured  juice  contained  no  dissolved  copper.  The 
maximum  amount  of  copper  allowed  by  the  United  States  Department 
of  Agriculture  in  gelatin  is  thirty-six  parts  per  million ;  in  most  other 
food  products,  no  copper  is  allowed.  Whether  the  Department  will 
rule  against  the  presence  of  small  amounts  of  copper  in  grape  syrup 
is  a  question  yet  to  be  decided.  Because  the  Department  is  desirous 
of  promoting  all  new  industries  that  will  utilize  wine  grapes,  it  is 
believed  that  if  the  amounts  of  copper  in  the  syrup  are  very  small,  no 
adverse  action  will  be  taken  during  the  first  season  at  least.  A  similar 
situation  exists  in  regard  to  small  amounts  of  copper  in  tomato 
products. 

The  interior  of  the  pan  may  be  silver-plated  at  a  moderate  expense. 
This  metal  is  insoluble  in  untreated  grape  juice  but  dissolves  rapidly 
in  juice  containing  sulfurous  acid.  Tin  linings  are  often  used  but  tin 
dissolves  in  the  juice  rather  rapidly  and  must  be  replaced  in  time. 
Retinning  is  extremely  difficult  for  the  special  tubes  used  in  such  pans. 

A  good  suggestion  made  by  one  vacuum  pan  manufacturer  is  to 
make  the  body  of  the  pan  of  very  heavily  tinned  or  silver-plated 
copper  and  the  boiling  coils  of  Monel  metal,  nickel,  or  aluminum,  all 
of  which  are  insoluble  in  the  juice.  Aluminum,  however,  in  time 
becomes  pitted.  Monel  metal  is  insoluble  and  of  high  tensile  strength, 
although  somewhat  more  expensive  than  copper.  Glass-lined  vacuum 
pans  may  be  used  satisfactorily,  although  the  evaporating  capacity 
should  be  increased  by  installing  inside  the  pan  a  Monel  metal  or  other 
insoluble  steam  coil. 

Loss  of  Juice  hy  Frothing. — The  pan  should  be  deep  enough  or 
equipped  with  a  trap  to  prevent  loss  of  juice  or  syrup  by  frothing. 

Syrup  hy  Freezing. — The  process  described  above  results  in  loss  of 
much  of  the  fresh  grape  flavor.  By  means  of  a  process  developed  by 
H.  C.  Gore  of  the  United  States  Department  of  Agriculture,  it  is  pos- 
sible to  retain  practically  all  of  the  fresh  flavor  in  concentrated  form 
in  the  finished  product.    The  Gore  process  is  carried  out  as  follows : 

The  juice  is  frozen  to  a  solid  mass  at  10-15  degrees  Fahrenheit.  It 
is  then  broken  in  an  ice-crushing  machine.  The  crushed  ice  is  placed 
in  an  ordinary  sugar  centrifuge  and  the  syrup  separated  from  the  ice 
by  centrifugal  force.  The  syrup  is  thrown  through  the  small  holes  of 
the  centrifuge  basket  and  the  ice  remains  in  the  centrifuge.  The 
syrup  so  obtained  is  again  frozen  at  0-10  degrees  Fahrenheit  to  a 
mushy  mass  of  ice  crystals  and  syrup.  By  centrifuging  this  mixture 
a  syrup  of  50  to  60  degrees  Balling  is  obtained.  A  small  amount 
(about  1  per  cent)  of  sugar  is  lost  in  the  ice.  Gore's  work  was  done 
upon  apple  juice. 


Bulletin  321         COMMERCIAL  PRODUCTION  OP  GRAPE  SYRUP  413 

The  writer  repeated  Gore's  experiments  with  Muscat  grape  juice 
instead  of  apple  juice.  A  syrup  of  55  degrees  Balling  was  as  rich  as 
it  was  found  feasible  to  produce  with  the  available  equipment.  The 
syrup  was  therefore  not  sweet  enough  for  general  use  and  would 
ferment  quickly  unless  sterilized.  Even  a  60  degree  Balling  syrup  is 
too  '^thin"  and  will  not  keep  long.  A  60  degree  Balling  syrup  is  the 
vsweetest  syrup  recorded  as  having  been  produced  by  this  process. 

Therefore,  it  was  found  necessary  to  blend  with  this  syrup  obtained 
by  freezing,  a  syrup  of  70-75  degrees  Balling  made  in  an  ordinary 
vacuum  pan.  The  blend  of  65  degrees  Balling  was  very  rich  in  flavor 
and  far  superior  to  any  syrup  that  had  previously  come  to  the  writer's 
attention. 

Second  crop  Muscat  grapes,  which  formerly  were  used  for  wine 
making,  and  can  not  be  sun  dried  because  of  late  ripening,  would  make 
an  excellent  syrup  for  blending  purposes. 

It  was  noted  that  the  ice  left  in  the  centrifuge  was  sour  in  taste. 
When  melted  it  was  found  to  contain  "%oo  of  one  per  cent  of  cream 
of  tartar  and  a  similar  amount  of  sugar.  On  concontration  of  a  sample 
of  this  liquid  to  a  small  volume  most  of  the  cream  of  tartar  was 
recovered  in  a  quite  high  state  of  purity.  This  suggests  the  possibility 
of  obtaining  cream  of  tartar  as  a  valuable  by-product. 

The  Gore  process  may  be  used  without  royalty  charges  because  it 
is  covered  by  a  public  service  patent  which  makes  the  process  public 
property.  It  is  stated  that  the  process  is  now  used  in  a  commercial 
wa,y  for  the  production  of  pineapple  syrup. 

PRESERVATION  OF  JUICE 

Juice  may  be  preserved  in  one  of  three  ways  for  shipment  to  a 
syrup  plant  or  storage  at  the  syrup  plant  until  needed. 

By  Pasteurization. — The  juice  may  be  heated  to  175°  to  185°  F., 
run  hot  into  sterilized  barrels,  and  sealed.  Most  of  the  juice  will  keep, 
although  some  loss  by  fermentation  will  result.  The  method  is  trouble- 
some and  expensive,  but  could  be  used  in  case  of  necessity. 

By  Freezing  Storage. — At  32°  F  grape  juice  will  ferment,  but  will 
keep  perfectly  at  15°  to  20°  F.  Large  breweries  are  equipped  with 
ample  cold-storage  facilities  which  might  be  used  in  conjunction  with 
syrup  factories  located  in  such  establishments.  The  fresh  juice  could 
be  chilled  by  passing  it  over  the  coolers  formerly  used  for  chilling 
beer  wort.  The  chilled  juice  could  be  stored  in  glass-lined  or  wooden 
tanks  formerly  used  for  beer,  and  could  be  removed  and  concentrated 
as  needed.  It  would  not  repay  other  prospective  manufacturers  of 
syrup  to  install  expensive  cold  storage  equipment. 


414  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

By  Use  of  Sulfur ous  Acid. — Fermentation  may  be  prevented  by  the 
addition  of  sulfurous  acid.  The  amount  necessary  in  hot  localities  is 
about  ^Yioo  to  ^%oo  of  one  per  cent.,  or,  expressed  in  usual  terms, 
1200  to  1500  miligrams  per  liter.  In  cooler  localities,  750  to  1000 
milligrams  per  liter  has  been  found  sufficient. 

Sulfurous  acid  may  be  had  in  several  forms,  such  as  a  6  per  cent 
solution  in  water;  or  as  the  liquefied  gas  which  is  almost  100  per  cent 
sulfurous  acid;  or  as  the  salts,  sodium  metabisulfite  and  potassium 
metabisulfite,  which  contain  about  50  per  cent  sulfurous  acid. 

The  addition  of  11^2  gallons  of  6  per  cent  sulfurous  acid  per  1000 
gallons  of  juice  corresponds  to  approximately  %o  of  1  psr  cent  sulfurous 
acid.  This  corresponds  to  approximately  16  to  17  pounds  of  sodium 
or  potassium  metabisulfite  per  1000  gallons  of  juice.  If  either  of  these 
salts  is  used  it  should  first  be  dissolved  in  water ;  for  example,  at  the 
rate  of  one  pound  per  gallon.  The  sulfurous  acid  must  be  mixed 
thoroughly  with  the  juice ;  this  can  be  done  by  stirring  with  a  wooden 
paddle  or  by  compressed  air.  Metal  should  not  be  permitted  to  come 
in  contact  with  freshly  treated  juice. 

The  juice  should  be  cooled  to  70°  F.  or  less,  if  possible,  before 
storage  to  insure  the  best  results.  Artificial  cooling  of  juice  from 
heated  grapes  will  probably  be  necessary.  The  cooler  the  juice  the 
less  sulfurous  acid  is  needed  to  preserve  it.  In  our  experimental  work 
with  50-gallon  lots,  juice  has  been  held  for  two  years  with  ^%oo  of 
1  per  cent  of  sulfurous  acid. 

Juice  containing -sulfurous  acid  must  be  treated  to  remove  as  much 
of  this  preservative  as  possible  before  the  juice  is  made  into  syrup. 
One  method  suggested  and  tested  has  been  to  heat  the  treated  juice 
to  160°  F.  and  pass  a  stream  of  air  through  it  at  this  temperature. 
In  small  laboratory  tests  most  of  the  sulfurous  acid  can  be  removed 
in  this  way,  but  upon  a  large  scale  the  results  have  not  been  very 
satisfactory.  The  passing  of  steam  through  the  boiling  juice  in 
the  open  air  removes  the  sulfurous  acid  more  rapidly  than  does  a 
current  of  air;  steam  passed  through  the  juice  in  a  vacuum  pan 
removes  the  sulfurous  acid  the  most  rapidly  of  any  method  tested,  but 
the  method  offers  mechanical  difficulties  when  applied  on  a  large  scale. 
Dry  steam  must  be  used  and  the  juice  must  be  kept  at  the  boiling  point 
during  the  passage  of  steam  to  prevent  a  great  increase  in  volume  by 
condensation. 

Simple  concentration  in  a  vacuum  pan  will  remove  a  large  amount 
of  the  sulfurous  acid,  as  the  following  typical  test  by  R.  W.  Bettoli 
will  show:    The  origanal  juice  contained  1288  milligrams  of  sulfurous 


Bulletin  321  COMMERCIAL  PRODUCTION  OP  GRAPE  SYRUP  415 

acid  per  liter.  It  was  concentrated  to  a  syrup  of  70°  Balling  under 
a  vacuum.  After  concentration  the  finished  syrup  contained  only 
420  milligrams.  Allowing  a  concentration  of  3  to  1,  this  syrup  after 
diluting  with  water  to  the  original  Balling  degree  of  the  juice  would 
contain  only  140  milligrams  of  sulfurous  acid,  indicating  that  about 
90  per  cent  of  the  sulfurous  acid  was  removed  during  the  concen- 
tration. These  results  were  confirmed  by  large-scale  experiments  by 
Mr.  Bettoli  and  by  laboratory  tests  by  the  writer. 

A  much  better  syrup  can  be  made  from  the  fresh  untreated  juice 
than  from  juice  containing  sulfurous  acid.  The  removal  of  the  sul- 
furous acid  is  incomplete  and  troublesome.  Juice  containing  sulfurous 
acid  is  corrosive  and  attacks  both  copper  and  silver,  necessitating  the 
use  of  glass-lined  or  Monel  metal  or  other  resistant  vacuum  pans. 
For  these  reasons  it  is  strongly  advised  that  vacuum  pans  of  sufficient 
size  be  installed  to  concentrate  the  juice  from  the  grapes  as  rapidly 
as  they  are  received;  thus  avoiding  the  necessity  of  using  sulfurous 
acid.  In  other  words,  our  advice  is  ''Do  not  use  sulfurous  acid  if  it 
can  possibly  be  avoided. ' ' 


SUMMARY 

1.  As  a  result  of  laboratory  and  commercial  experiments  in  grape 
syrup  manufacture  it  is  believed  that  a  syrup  of  deep  red  color  and 
rich  berry-like  flavor  will  give  the  best  results  from  a  commercial 
standpoint  during  the  coming  season.  Other  types  of  syrup  with  a 
larger  amount  of  fresh  grape  flavor  may  in  time  supersede  the  type 
of  syrup  recommended  above. 

2.  Large  wineries  already  possess  all  necessary  equipment  for  grape 
syrup  manufacture  except  vacuum  pans.  Grape  syrup  manufacture 
can  more  readily  be  undertaken  by  such  establishments  than  by  small 
wineries.  Milk  canneries  now  equipped  with  large  vacuum  pans 
might  well  consider  grape  syrup  manufacture  as  a  profitable  side  line. 
Breweries,  because  of  their  large  cold-storage  capacity,  steam  plants, 
filtering  equipment,  etc.,  may  easily  be  converted  into  grape  syrup 
factories. 

3.  Vacuum  pans  should  be  constructed  of  materials  not  soluble  in 
the  juice.  Copper  has  been  the  most  common  material  employed,  but 
analyses  show  that  small  amounts  of  this  metal  may  dissolve  in  the 
juice  during  concentration.  Therefore,  the  use  of  copper  vacuum  pans 
might  in  time  conflict  with  the  Pure  Food  regulations,  and  make  the 
use  of  a  material  about  which  there  is  no  doubt,  highly  desirable. 


416  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT   STATION 

4.  Syrup  should  be  concentrated  to  68° to  70°  Balling  if  it  is  to 
be  kept  without  sterilization. 

5.  The  use  of  a  high  vacuum  of  28  to  29  inches  during  concentra- 
tion prevents  injury  to  the  flavor  and  color  of  the  syrup  by  heat. 

6.  The  syrup  should  be  cooled  after  concentrating  to  avoid  injury 
to  color  and  flavor  of  the  syrup. 

7.  Grape  syrup  has  a  great  many  different  uses  and  its  manufac- 
ture presents  one  of  the  most  promising  methods  of  profitably  utilizing 
the  crop  of  wine  grapes  of  the  state. 


STATION  PUBLICATIONS  AVAILABLE  FOE  FREE  DISTRIBUTION 


BULLETINS 


No. 

168.  Observations   on    Some   Vine   Diseases 

in   Sonoma   County. 

169.  Tolerance  of  the  Sugar  Beet  for  Alkali. 
185.   Report  of  Progress  in  Cereal  Investi- 
gations. 

208.   The  Late  Blight  of  Celery. 
230.   Enological  Investigations. 

250.  The  Loquat. 

251.  Utilization  of  the  Nitrogen  and  Organic 

Matter   in    Septic    and    Imhoff   Tank 
Sludges. 

252.  Deterioration  of  Lumber. 

253.  Irrigation   and   Soil   Conditions  in   the 

Sierra   Nevada   Foothills,    California. 
257.   New   Dosage   Tables. 

261.  Melaxuma    of    the    Walnut,     "Juglans 

regia." 

262.  Citrus   Diseases   of   Florida    and   Cuba 

Compared  w^ith  Those  of  California. 

263.  Size  Grades  for  Ripe  Olives. 

266.  A  Spotting  of  Citrus  Fruits  Due  to  the 

Action    of    Oil    Liberated    from    the 
Rind. 

267.  Experiments  with  Stocks  for  Citrus. 

268.  Growing  and  Grafting  Olive  Seedlings. 

270.  A  Comparison  of  Annual  Cropping,  Bi- 

ennial Cropping,  and  Green  Manures 
on  the  Yield  of  Wheat. 

271.  Feeding  Dairy  Calves  in  California. 

272.  Commercial  Fertilizers. 

273.  Preliminary  Report  on  Kearney  Vine- 

yard Experimental  Drain. 

274.  The  Common  Honey  Bee  as  an  Agent 

in  Prune  Pollination. 

275.  The  Cultivation  of  Belladonna  in  Cali- 

fornia. 

276.  The  Pomegranate. 

277.  Sudan  Grass. 

278.  Grain   Sorghums. 

279.  Irrigation  of  Rice  in  California. 

280.  Irrigation  of  Alfalfa  in  the  Sacramento 

Valley. 

281.  Control  of  the  Pocket  Gopher  in  Cali- 

fornia. 

282.  Trials  with  California  Silage  Crops  for 

Dairy  Cows. 


No. 

283. 
285. 
286. 
288. 

290. 

293. 
296. 
297. 
298. 
299. 

300. 
301. 

302. 

303. 
304. 

305. 

307. 
308. 


309. 

310. 
311. 
312. 
313. 

314. 
316. 
317. 

318. 
319. 
320. 
321. 
322. 


The  Olive  Insects  of  California. 

The  Milch  Goat  in  California. 

Commercial  Fertilizers. 

Potash  from  Tule  and  the  Fertilizer 
Value  of  Certain  Marsh  Plants. 

The  June  Drop  of  Washington  Navel 
Oranges. 

Sweet   Sorghums  for  Forage. 

Topping  and  Pinching  Vines. 

The  Almond  in  California. 

Seedless  Raisin  Grapes. 

The  Use  of  Lumber  on  California 
Farms. 

Commercial  Fertilizers. 

California  State  Dairy  Cow  Competi- 
tion, 1916-18. 

Control  of  Ground  Squirrels  by  the 
Fumigation  Method. 

Grape  Syrup. 

A  Study  on  the  Effects  of  Freezes  on 
Citrus  in  California. 

The  Influence  of  Barley  on  the  Milk 
Secretion  of  Cows. 

Pollination  of  the  Bartlett  Pear. 

I.  Fumigation  with  Liquid  Hydrocianic 
Acid.  II.  Physical  and  Chemical 
Prorierties  of  Liquid  Hydrocianic 
Acid. 

I.  The  Carob  in  California.  II.  Nutri- 
tive Value  of  the  Carob  Bean. 

Plum  Pollination. 

Investigations  with  Milking  Machines. 

Mariout  Barley. 

Pruning  Young  Deciduous  Fruit 
Trees. 

Cow-Testing  Associations  in  California. 

The  Kaki  or  Oriental  Persimmon. 

Selection  of  Stocks  in  Citrus  Propaga- 
tion. 

The  Effects  of  Alkali  on  Citrus  Trees. 

Caprifrgs  and  Caprification. 

Control  of  the  Coyote  in  California. 

Commercial  Production  of  Grape  Syrup. 

The  Evaporation  of  Grapes. 


No. 
50. 
65. 
70. 

76. 
82. 

87. 
109. 


110. 
111. 

113. 
114. 
115. 
117. 

124. 
126. 
127. 
128. 
129. 
130. 
131. 
133. 


Fumigation   Scheduling. 

The  California  Insecticide  Law. 

Observations  on  the  Status  of  Corn 
Growing  in  California. 

Hot  Room  Callusing. 

The  Common  Ground  Squirrels  of 
California. 

Alfalfa. 

Community  or  Local  Extension  Work 
by  the  High  School  Agricultural  De- 
partment. 

Green  Manuring  in  California. 

The  Use  of  Lime  and  Gypsum  on  Cali- 
fornia  Soils. 

Correspondence  Courses  in  Agriculture 

Increasing  the  Duty  of  Water. 

Grafting  Vinifera  Vineyards. 

The  Selection  and  Cost  of  a  Small 
Pumping  Plant. 

Alfalfa  Silage  for  Fattening  Steers. 

Spraying  for  the  Grape  Leaf  Hopper. 

House  Fumigation. 

Insecticide  Formulas. 

The  Control  of  Citrus  Insects. 

Cabbage  Growing  in  California. 

Spraying  for  Control  of  Walnut  Aphis. 

County  Farm  Adviser. 


CIRCULARS 

No. 
135. 
136. 
137. 
138. 
139. 


140. 


143. 

144. 
147. 
148. 
152. 

153. 

154. 

155. 
156. 
157. 
158. 
159. 
160. 


Official  Tests  of  Dairy  Cows. 

Melilotus  Indica. 

Wood  Decay  in  Orchard  Trees. 

The  Silo  in  California  Agriculture. 

The  Generation  of  Hydrocyanic  Acid 
Gas  in  Fumigation  by  Portable 
Machines. 

The  Practical  Application  of  Improved 
Methods  of  Fermentation  in  Califor- 
nia Wineries  during  1913  and  1914. 

Control  of  Grasshoppers  in  Imperial 
Valley. 

Oidium  or  Powdery  Mildew  of  the  Vine. 

Tomato  Growing  in  California. 

"Lungworms". 

Some  Observations  on  the  Bulk  Hand- 
ling of  Grain  in  California. 

Announcement  of  the  California  State 
Dairy  Cow  Competition,  1916-18. 

Irrigation  Practice  in  Growing  Small 
Fruits  in  California. 

Bovine  Tuberculosis. 

How  to  Operate  an  Incubator. 

Control  of  the  Pear  Scab. 

Home  and  Farm  Canning. 

Agriculture  in  the  Imperial  Valley. 

Lettuce  Growing  in  California. 


CIRCULARS — Continued 


No.  No. 

164.  Small  Fruit  Culture  in  California.  191. 

165.  Fundamentals   of   Sugar   Beet   Culture  193. 

under  California  Conditions.  195. 

167.  Feeding  Stuffs  of  Minor  Importance. 

168.  Spraying    for    the     Control    of     "Wild  197. 

Morning-Glory  within  the  Fog  Belt. 

169.  The    1918   Grain   Crop.  198. 

170.  Fertilizing    California     Soils    for    the  199. 

1918   Crop.  201. 

172.  Wheat  Culture.  202. 

173.  The    Construction    of    the    Wood-Hoop 

Silo.  203. 

174.  Farm  Drainage  Methods.  204. 

175.  Progress  Report  on  the  Marketing  and 

Distribution  of  Milk.  205. 

176.  Hog  Cholera  Prevention  and  the  Serum  206. 

Treatment.  207. 

177.  Grain    Sorghums.  208. 

178.  The  Packing  of  Apples  in  California. 

179.  Factors   of     Importance   in    Producing  209. 

Milk  of  Low  Bacterial   Count.  210. 

181.  Control     of      the     California     Ground  213. 

Squirrel.  214. 

182.  Extending  the  Area  of  Irrigated  Wheat 

in  California  for  1918.  215. 

183.  Infectious  Abortion  in   Cows.  216. 

184.  A  Flock  of  Sheep  on  the  Farm. 

185.  Beekeeping   for   the   Fruit-grower    and  217. 

Small  Rancher  or  Amateur. 

187.  Utilizing  the   Sorghums.  218. 

188.  Lambing  Sheds. 

189.  Winter  Forage  Crops.  219. 

190.  Agriculture  Clubs  in   California.  220. 


Pruning  the  Seedless  Grapes. 

A  Study  of  Farm  Labor  in  California. 

Revised  Compatibility  Chart  of  Insecti- 
cides and  Fungicides. 

Suggestions  for  Increasing  Egg  Produc- 
tion in  a  Time  of  High-Feed  Prices. 

Syrup  from  Sweet  Sorghum. 

Onion  Growing  in  California. 

Helpful  Hints  to  Hog  Raisers. 

County  Organization  for  Rural  Fire 
Control. 

Peat  as  a  Manure  Substitute. 

Handbook  of  Plant  Diseases  and  Pest 
Control. 

Blackleg. 

Jack  Cheese. 

Neufchatel  Cheese. 

Summary  of  the  Annual  Reports  of  the 
Farm  Advisors  of  California. 

The  Function  of  the  Farm  Bureau. 

Suggestions  to  the  Settler  in  California. 

Evaporators  for  Prune  Drying. 

Seed  Treatment  for  the  Prevention  of 
Cereal  Smuts. 

Feeding  Dairy  Cows  in  California. 

Winter  Injury  or  Die-Back  of  the  Wal- 
nut. 

Methods  for  Marketing  Vegetables  in 
California. 

Advanced  Registry  Testing  of  Dairy 
Cows, 

The  Present  Status  of  Alkali. 

Unfermented  Fruit  Juices. 


